One wire any one

[be80be]

I'm working on a chip to put on a one wire bus. My idea is to use a small pic12f chip.

What I'm thinking is this put id on these chips one or two to start and make them send data just like a DS one wire chip.

What I want is to use them to turn things on using one wire.

What I'm asking is this the right timing

1 the master sends a 480uS Low reset then waits for the slave.
2 the slave sends after the line goes high for about 15uS a 60 uS low to let the master know it's there.
3 the master sends a 15 uS pulse which the slave then leave the line high for a 1 or pulls low for a 0 for each bit it sends. At 60uS a pop.

Have I missed anything here thanks for any input. Burt

 

[Mr RB]

...
1 the master sends a 480uS Low reset then waits for the slave.
2 the slave sends after the line goes high...
...

And if (when) you have more than one slave? They will all talk at once.

There is a system here for almost unlimited devices on a single serial wire;
https://www.romanblack.com/blacknet/blacknet.htm

that provides sequencing of all the devices so there are no conflicts.

 

[be80be]

Thanks MrRB looks nice but I'm going for true one-wire that could be used with a DS18B20 in the mix.

 

[Ian Rogers]

Thanks MrRB looks nice but I'm going for true one-wire that could be used with a DS18B20 in the mix.

If you have Oshonsoft... Just make all the routines... Compile... Hey presto... All the protocol in ASM ( software protocol. )

 

[be80be]

See I'm thinking I no there are DS one-wire output devices that can act like switches but not really able to sink much power, from What I see. So I'm thinking small pic 12f that knows how to keep it's mouth shut. LOL

This would let me read a DS18f20 and if it's cold outside turn the heat on in the dog house. Or if it's night give me some lights or a lot of lights. Or I'm at work headed home fix me some coffee with a call home. Got to be useful for some things.

I really liked MrRb blacknet idea too but I can't use a DS18F20 without adding more in the mix

Ian I use Oshonsoft a lot really want to buy the hole ball of wax. But work is slow been repairing old dryer boards with old intel 8049 in them serial adc VT seven segments lots of fun figuring how to make a replacement. Done deal now I didn't think it would be to hard to match that chip with a Pic18F2520 but it can handle the seven segment read the temp keep dryer 170 and count your money all at the same time almost.

 

[Pommie]

The problem with implementing OW in a 12 bit chip is making sure you don't miss a zero time slot. Zero slots can be low for as short as 1uS and so are easily missed in a software loop. One of the newer chips like the 12f683 (14 bit) would be able to do it using an edge triggered input. Implementing the SearchROM routine is going to be fun. Good luck with that.

Mike.

 

[be80be]

Yep Mike that looks like the hard part "Implementing the SearchROM routine" I was hoping to be able to leave that out. Just kidding, It's the part I really don't fully understand yet. Working on it. And I'm open any pointers anyone has.

See I first had this Idea load a pic with code to act like any one-wire device be good for testing ideas on the bus without owning a bunch of devices. But now I think I'll try it with output devices.

Back to reading about one-wire bus Thanks all for your input.

 

[Pommie]

Maxim have a very good article on the SearchROM algorithm. See this document.

Mike.

 

[be80be]

Thanks Mike I'm reading it now

 

[DirtyLude]

The enhanced 12f chips have a eusart and support LIN.

 

[Mr RB]

I would use a PIC for every node, 12F PICs are cheap. Then any temperature sensor (or other sensors) you like on that node. The PICs do all the coms. Personally I think the Dallas 1-wire protocol sucks, and would prefer something slower datarate (more reliable data) and a lot less data needing to be sent (ie device numbers as 8 bit not zillions of bits).

 

[be80be]

Roman I agree DS sucks there to muck data being sent on the line. I really liked your idea and going to play with it too. But my DS idea is to make some $$$ off the arduino as a addon to the DS bus

 

[3v0]

Dallas does make 1 wire switches. Use them to drive a transistor if you need more power. But there is a possibility they have been obsoleted. I have 50 of them here somewhere.

The plan is to use them to control triacs to switch my shop lights on and off.